This invention relates to a timing belt tensioner for an engine, and more particularly to an improved, simplified, and more easily adjustable timing belt tensioner for an engine.
In internal combustion engines, and particularly those operating on a four-cycle principle, it is the practice to drive the camshaft or camshafts of the engine by means of a timing drive mechanism. Frequently, either timing belts or timing chains, hereinafter referred to collectively as "flexible transmitters," are normally employed for this purpose. Where flexible transmitters are employed for driving a camshaft from an engine crankshaft, however, it is necessary to provide some mechanism for adjusting the tension on the flexible transmitter. This is because the transmitters tend to elongate with time, and unless the appropriate tension is maintained on the transmitter, the driving relationship between the transmitter, the crankshaft, and the camshaft can become disturbed.
It is normally the practice to employ an idler pulley that is engaged with the flexible transmitter and which is adjustably supported for achieving the tensioning adjustment. Normally, this idle tensioner pulley is positioned close to the driving sprocket on the crankshaft. The reason for this is to ensure that the flexible transmitter be it a chain or a toothed belt is maintained in engagement with a substantial portion of the driving sprocket.
This gives rise to certain problems in conjunction with the periodic adjustment of the tensioner. These problems are particularly acute when the mechanism is employed as a power plant in an outboard motor. Normally, in outboard motor applications and also in many other applications for engines, there is attached to the crankshaft a flywheel which is disposed outwardly of the driving sprocket for the camshaft drive. As a result, the tensioner pulley will be positioned within the peripheral edge of the flywheel, and thus it may be necessary to remove the flywheel in order to provide access to the adjustment mechanism of the tensioner. Obviously, this is a time-consuming and cumbersome task.
It is, therefore, a principal object of this invention to provide an improved tensioner arrangement for the camshaft drive of an internal combustion engine.
It is a further object of this invention to provide an improved tensioner arrangement for the flexible transmitter of a camshaft drive wherein the tensioner pulley is positioned within the outer peripheral edges of the flywheel, but its adjustment can be affected without removal of the flywheel.